1. Field of the Invention
The present invention relates to a carrier for immobilization of animal cells, a process for manufacturing the carrier, and a method for cultivating the animal cells using the carrier.
2. Description of the Related Art
Mass production of pharmaceutically useful substances having a physiological activity is carried out by cultivating animal cells etc. The animal cells used for the cultivation include anchorage independent cells which exist in a floating state, such as blood cells and cancer cells, and anchorage dependent cells which exist adhered to a suitable carrier. It is advantageous to use floating cells (anchorage independent cells) for the efficient production of physiologically active substances. Therefore, there exists a method for selecting mutant or variant strains which can proliferate in a floating state among anchorage dependent cells to be used. Nevertheless, it is not possible to utilize the above method for all anchorage dependent cells. Accordingly, there is a demand for a suitable carrier which can be adhered to by anchorage dependent cells.
Recently, mass production of physiologically active substances is practically carried out, using recombinants, i.e., cells or microorganisms transformed by genetic recombinant techniques. When the physiologically active substances are manufactured by the recombinants, glycosylated proteins such as vaccines and antibiotics can not be obtained from recombinant microorganisms, but from recombinant animal cells. Therefore, it is considered easier to obtain useful physiologically active substances from animal cell products rather than microbial products, so it is expected that animal cells will be used in more cases. Adhesive property of animal cells, however, tends to be lowered by gene manipulation, so in this respect, development of a material superior in cell adhesion is desired.
As a carrier for immobilization of anchorage dependent cells, microcarriers having a substrate of porous beads, such as cellulose, chitosan or silane, were known. Such microcarriers had the large specific surface area per volume, and thus were considered particularly suitable for cultivation in an industrial scale. Nevertheless, the conventional microcarriers not only were prepared by complicated processes and thus expensive, but also not necessarily easy for cells to adhere to the individual beads. Further, the shearing force produced during agitation in the culture tanks damaged the cells, and careful handling was required.
Further, an immobilization Carrier prepared by coating collagen on various types of substrates was known. However, the above immobilization carrier had the defect that the sterilization treatment in an autoclave which should be carried out before immobilizing the animal cells caused flowing off of the collagen layer from the carrier and deterioration of the collagen per se, and so a reduction in the adhesive property. There existed some methods of sterilization treatment other than the above treatment in an autoclave, but these methods required special equipment or were accompanied with risk, and so were not able to be generally used.